The present application generally relates to methods of treating animals, including humans. More particularly, it relates to methods of treating animals to selectively alter body fat, feed efficiency, or weight gain (which can also be measured as growth rate).
CLA is a mixture of isomers that can be formed from 9c,12c-octadecadienoic acid (linoleic acid) which can, theoretically, be autoxidized or alkali-isomerized into 8 conjugated geometric isomers of 9,11- and 10,12-octadecadienoic acid (9c,11c; 9c,11t; 9t,11c; 9t,11t; 10c,12c; 10c,12t; 10t,12c and 10t,12t). The role or roles of individual isomers in particular effects was not previously known because the CLA evaluated in prior studies was a mixture of 9,11-octadecadienoic acids and 10,12-octadecadienoic acids and other CLA isomers. It would be advantageous to clarify these aspects of CLA activity to facilitate preparing novel compositions for administering to animals to maintain a desired biological activity while reducing an undesired activity.
Prior commercial preparations of CLA isomers made from vegetable oil for administration to animals (e.g., CLA-60) typically contain about 20% 10t, 12c-CLA, about 14% 9c, 11t-CLA, and about 66% total CLA isomers. The ratio of 9c, 11t-CLA to 10t, 12c-CLA in such preparations is about 0.7. Other preparations, such as CLA-95 made from 95% linoleic acid, have slightly different isomer ratios. CLA synthesized from linoleic acid or from linoleic-rich oils tend to have ratios of 9c, 11t-CLA to 10t, 12c-CLA of less than 1:1, typically 0.6-0.97 to 1. Such preparations typically contain more 10t, 12c-CLA than 9c, 11t-CLA.
U.S. Pat. No. 5,428,072 discloses a method for increasing the efficiency of converting feed to body weight in an animal which comprises administering to the animal an amount of a conjugated linoleic acid (CLA) mixture effective to increase the efficiency of feed conversion to body weight in the animal.
U.S. Pat. No. 5,554,646 discloses a method for reducing the amount of body fat in an animal by administering to the animal an amount of a CLA mixture effective to reduce the amount of body fat in the animal.
Animals fed standard preparations of CLA consistently gain less weight than non-CLA fed controls. This can be a commercial disadvantage, in that it is often desirable to increase weight gain and rate of gain in animals raised to be food sources. This effect of CLA can be seen in numerous papers including, for example, Wong, M. W., et al., Anticancer Research 17:987-994 (1997); Hayek, M. G., et al., J. Nutr. 129:32-38 (1999); West, D. B., et al., Am. J. Physiol. 275 (Regulatory Integrative Comp. Physiol. 44): R667-R672 (1998); Cesano, A., et al., Anticancer Research 18:1429-1434 (1998).
Park, Y. et al, "Effect of Conjugated Linoleic Acid on Body Composition in Mice," Lipids 32:853 (1997) observed reduced body fat and increased lean body mass in mice fed a mixture of CLA isomers, relative to control animals fed corn oil, where the mixture contained approximately equal percentages of the major CLA isomers, namely 9-cis, 11-trans-CLA and 10-trans, 12-cis-CLA. Despite this apparent showing, it is important to note that Park, et al. selected animals having a similar body weight in the reported experiments to avoid introducing changed body weight as a variable in the analysis. Even so, those authors saw slightly reduced body weight in female mice relative to controls.